Elektor Team
About the article

Sand Clock

A real eye-catcher

Sand Clock
This nifty gadget built around an Arduino Uno uses some servos and a pantograph mechanism to write the time in a sand bed. After a configurable time interval the sand is smoothed out by a pair of vibration motors and the cycle starts over again. Along with the automatic time mode, the clock software has a command mode which allows you to control the pen using simple commands.
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Component list
Component List
R1,R2,R3 = 220Ω, SMD 0805
R4 = 1.8kΩ, SMD 0805
R5–R9 = 4.7kΩ, SMD 0805
R10 = 100kΩ, SMD 0805

C1–C4 = 100nF, SMD 0805 MLCC
C5 = 10µF 10V, SMD 1206 MLCC
C6 = 22µF 16V

D1,D2,D3 = S2J-E3
T1 = BCX56
IC1 = SIP3 5V/1A DC/DC converter (Würth Elektronik # 173 010 578)
IC2 = PCF2129A

K1 = set of SIL pinheaders, 0.1’’ pitch (1 pc. 10-pin, 2 pc. 8-pin, 1 pc. 6-pin)
SERVO_Z,SERVO_L,SERVO_R = 3-ppin right-angled pinheader, 0.1’’ pitch
B1 = CR2032 button cell with holder
Arduino UNO R3 or equivalent

Mechanical parts
6 pcs. bolt, M2x10, Pozidrive/Phillips
6 pcs. bolt, M2.5x8, zinc-plated steel, Pozidrive DIN 7985A
6 pcs. bolt, M2.5x12, zinc-plated steel, Pozidrive DIN 7985A
2 pcs. bolt, M3x6, zinc-plated steel, Pozidrive DIN 7985A
2 pcs. bolt, M3x8, zinc-plated steel, Pozidrive DIN 7985A
15 pcs. bolt, M3x10, zinc-plated steel, Pozidrive DIN 7985A
1 pc. bolt M4x30 plastic, Phillips (sharpen end with pencil sharpener)
6 pcs. nut, M2, zinc-plated steel, DIN 934
7 pcs. nut, M3, steel, DIN 934
3 pcs. locking nut, M3, zinc-plated steel, DIN 985
1 pc. nut, M4, polyamide
2 pcs. washer, M3, zinc-plated steel, DIN 125A
4 pcs. washer, M3, plastic, DIN 125A
4 pcs. standoff, 3mm high, polyamide, for M3
4 pcs. spacer, 25mm, M/F M3, nickel-plated brass (min. 33mm total height, e.g. TME TFM-M3X25/DR213)
2 pcs. cable clip, polyamide, Panduit type CCS25-S10-C
4 pcs. self-adhesive rubber foot
3 pcs. micro servo, Tower Pro MG90S of MG90 with metal cogs
2 pcs. vibration motor, round, 6mm diam., type VM6ZK273 (JPR Electronics # 450-007)
Extruded (XT) PMMA, 3mm, clear, laser-cut
Fine-grain white sand (see text)
Nourishment coloring additive (optional)

A DIY kit including all parts and the SMD-preassembled shield is available through the Elektor Store.
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